def caesar(code, shift):
  ''' (str, int) -> str
  Shift every letter in the code by the integer 'shift'.
  >>> caesar('ABC', 2)
  CDE
  >>> caesar('a b c', 4)
  e f g
  '''
  decipher = ''
  for char in code:
    if 65<=ord(char)<=90:
        decipher = decipher + chr((ord(char) - 65 + shift)%26+65)
    if 97<=ord(char)<=122:
        decipher = decipher + chr((ord(char) - 97 + shift)%26+97)
    else:
      decipher += char
  return decipher
print(caesar('ABC', 2))
print(caesar('a b c', 4))

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